To increase the speed of wireless communication of smartphones and mobile phones, technology for simultaneously using a plurality of bands such as Carrier Aggregation has been used. Thus, a multiplexer is used. In the multiplexer, first ends of a plurality of low-pass filters (LPFs), bandpass filters (BPFs) and/or high-pass filters (HPFs) are commonly coupled to a common terminal as disclosed in, for example, Japanese Patent Application Publication Nos. 2015-115866, 2006-332980, and 2011-91862.